1. Field of the Invention
The present invention relates to control devices for rotating electrical machines of a field winding type, which is capable of controlling the operation of the rotating electrical machine.
2. Description of the Related Art
In addition to an internal combustion engine, a rotating electrical machine of a field winding type is mounted on a motor vehicle capable of having both functions of an alternator and an electric motor. The alternator generates regenerative electric power. The electric motor generates and outputs a torque to be used for staring the internal combustion engine of the motor vehicle.
The field winding of such a rotating electrical machine having the functions of the alternator and the electric motor has a large time constant of a field current. That is, a long period of time is required for the rotating electric machine of a field winding type in order to increase a field current of the field winding thereof to an adequate value. Accordingly, the rotating electric machine of a field winding type has a low responsiveness to a requested torque.
In order to solve the conventional problem previously described, a patent document, Japanese patent laid open publication No. 2004-144019, discloses a rotating electrical machine having a structure in which an armature current flows in an armature winding in order to generate a magnetic flux, in a direction which is opposite to a field flux of the field current simultaneously or before the supply of the field current and eliminates a self-inductance of the field winding, and in order to perform electromagnetic induction in a direction to increase the field current.
Since the d-axis current has a low influence on an output torque of the rotating electric machine, the continuous flow of the d-axis current causes wastage of electrical power. The patent document 1 shows no suggestion to solve a problem caused by such a continuous flow of the d-axis current in the armature winding.